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Merge branch '1.6.1-SNAPSHOT'
Conflicts:
docs/src/main/asciidoc/chapters/administration.txt
Project: http://git-wip-us.apache.org/repos/asf/accumulo/repo
Commit: http://git-wip-us.apache.org/repos/asf/accumulo/commit/a66d074d
Tree: http://git-wip-us.apache.org/repos/asf/accumulo/tree/a66d074d
Diff: http://git-wip-us.apache.org/repos/asf/accumulo/diff/a66d074d
Branch: refs/heads/master
Commit: a66d074db29f4ce45cdecc88dc1708042780fac0
Parents: db72ba3 6d77c2d
Author: Josh Elser <elserj@apache.org>
Authored: Fri Aug 1 17:16:27 2014 -0400
Committer: Josh Elser <elserj@apache.org>
Committed: Fri Aug 1 17:16:27 2014 -0400
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+// Licensed to the Apache Software Foundation (ASF) under one or more
+// contributor license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright ownership.
+// The ASF licenses this file to You under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance with
+// the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+== Administration
+
+=== Hardware
+
+Because we are running essentially two or three systems simultaneously layered
+across the cluster: HDFS, Accumulo and MapReduce, it is typical for hardware to
+consist of 4 to 8 cores, and 8 to 32 GB RAM. This is so each running process can have
+at least one core and 2 - 4 GB each.
+
+One core running HDFS can typically keep 2 to 4 disks busy, so each machine may
+typically have as little as 2 x 300GB disks and as much as 4 x 1TB or 2TB disks.
+
+It is possible to do with less than this, such as with 1u servers with 2 cores and 4GB
+each, but in this case it is recommended to only run up to two processes per
+machine -- i.e. DataNode and TabletServer or DataNode and MapReduce worker but
+not all three. The constraint here is having enough available heap space for all the
+processes on a machine.
+
+=== Network
+
+Accumulo communicates via remote procedure calls over TCP/IP for both passing
+data and control messages. In addition, Accumulo uses HDFS clients to
+communicate with HDFS. To achieve good ingest and query performance, sufficient
+network bandwidth must be available between any two machines.
+
+In addition to needing access to ports associated with HDFS and ZooKeeper, Accumulo will
+use the following default ports. Please make sure that they are open, or change
+their value in conf/accumulo-site.xml.
+
+.Accumulo default ports
+[width="75%",cols=">,^2,^2"]
+[options="header"]
+|====
+|Port | Description | Property Name
+|4445 | Shutdown Port (Accumulo MiniCluster) | n/a
+|4560 | Accumulo monitor (for centralized log display) | monitor.port.log4j
+|9997 | Tablet Server | tserver.port.client
+|9999 | Master Server | master.port.client
+|12234 | Accumulo Tracer | trace.port.client
+|42424 | Accumulo Proxy Server | n/a
+|50091 | Accumulo GC | gc.port.client
+|50095 | Accumulo HTTP monitor | monitor.port.client
+|====
+
+In addition, the user can provide +0+ and an ephemeral port will be chosen instead. This
+ephemeral port is likely to be unique and not already bound. Thus, configuring ports to
+use +0+ instead of an explicit value, should, in most cases, work around any issues of
+running multiple distinct Accumulo instances (or any other process which tries to use the
+same default ports) on the same hardware.
+
+=== Installation
+Choose a directory for the Accumulo installation. This directory will be referenced
+by the environment variable +$ACCUMULO_HOME+. Run the following:
+
+ $ tar xzf accumulo-1.6.0-bin.tar.gz # unpack to subdirectory
+ $ mv accumulo-1.6.0 $ACCUMULO_HOME # move to desired location
+
+Repeat this step at each machine within the cluster. Usually all machines have the
+same +$ACCUMULO_HOME+.
+
+=== Dependencies
+Accumulo requires HDFS and ZooKeeper to be configured and running
+before starting. Password-less SSH should be configured between at least the
+Accumulo master and TabletServer machines. It is also a good idea to run Network
+Time Protocol (NTP) within the cluster to ensure nodes' clocks don't get too out of
+sync, which can cause problems with automatically timestamped data.
+
+=== Configuration
+
+Accumulo is configured by editing several Shell and XML files found in
++$ACCUMULO_HOME/conf+. The structure closely resembles Hadoop's configuration
+files.
+
+==== Edit conf/accumulo-env.sh
+
+Accumulo needs to know where to find the software it depends on. Edit accumulo-env.sh
+and specify the following:
+
+. Enter the location of the installation directory of Accumulo for +$ACCUMULO_HOME+
+. Enter your system's Java home for +$JAVA_HOME+
+. Enter the location of Hadoop for +$HADOOP_PREFIX+
+. Choose a location for Accumulo logs and enter it for +$ACCUMULO_LOG_DIR+
+. Enter the location of ZooKeeper for +$ZOOKEEPER_HOME+
+
+By default Accumulo TabletServers are set to use 1GB of memory. You may change
+this by altering the value of +$ACCUMULO_TSERVER_OPTS+. Note the syntax is that of
+the Java JVM command line options. This value should be less than the physical
+memory of the machines running TabletServers.
+
+There are similar options for the master's memory usage and the garbage collector
+process. Reduce these if they exceed the physical RAM of your hardware and
+increase them, within the bounds of the physical RAM, if a process fails because of
+insufficient memory.
+
+Note that you will be specifying the Java heap space in accumulo-env.sh. You should
+make sure that the total heap space used for the Accumulo tserver and the Hadoop
+DataNode and TaskTracker is less than the available memory on each slave node in
+the cluster. On large clusters, it is recommended that the Accumulo master, Hadoop
+NameNode, secondary NameNode, and Hadoop JobTracker all be run on separate
+machines to allow them to use more heap space. If you are running these on the
+same machine on a small cluster, likewise make sure their heap space settings fit
+within the available memory.
+
+==== Native Map
+
+The tablet server uses a data structure called a MemTable to store sorted key/value
+pairs in memory when they are first received from the client. When a minor compaction
+occurs, this data structure is written to HDFS. The MemTable will default to using
+memory in the JVM but a JNI version, called the native map, can be used to significantly
+speed up performance by utilizing the memory space of the native operating system. The
+native map also avoids the performance implications brought on by garbage collection
+in the JVM by causing it to pause much less frequently.
+
+32-bit and 64-bit Linux and Mac OS X versions of the native map can be built
+from the Accumulo bin package by executing
++$ACCUMULO_HOME/bin/build_native_library.sh+. If your system's
+default compiler options are insufficient, you can add additional compiler
+options to the command line, such as options for the architecture. These will be
+passed to the Makefile in the environment variable +USERFLAGS+.
+
+Examples:
+
+. +$ACCUMULO_HOME/bin/build_native_library.sh+
+. +$ACCUMULO_HOME/bin/build_native_library.sh -m32+
+
+After building the native map from the source, you will find the artifact in
++$ACCUMULO_HOME/lib/native+. Upon starting up, the tablet server will look
+in this directory for the map library. If the file is renamed or moved from its
+target directory, the tablet server may not be able to find it. The system can
+also locate the native maps shared library by setting +LD_LIBRARY_PATH+
+(or +DYLD_LIBRARY_PATH+ on Mac OS X) in +$ACCUMULO_HOME/conf/accumulo-env.sh+.
+
+==== Cluster Specification
+
+On the machine that will serve as the Accumulo master:
+
+. Write the IP address or domain name of the Accumulo Master to the +$ACCUMULO_HOME/conf/masters+
file.
+. Write the IP addresses or domain name of the machines that will be TabletServers in +$ACCUMULO_HOME/conf/slaves+,
one per line.
+
+Note that if using domain names rather than IP addresses, DNS must be configured
+properly for all machines participating in the cluster. DNS can be a confusing source
+of errors.
+
+==== Accumulo Settings
+Specify appropriate values for the following settings in
++$ACCUMULO_HOME/conf/accumulo-site.xml+ :
+
+[source,xml]
+<property>
+ <name>instance.zookeeper.host</name>
+ <value>zooserver-one:2181,zooserver-two:2181</value>
+ <description>list of zookeeper servers</description>
+</property>
+
+This enables Accumulo to find ZooKeeper. Accumulo uses ZooKeeper to coordinate
+settings between processes and helps finalize TabletServer failure.
+
+[source,xml]
+<property>
+ <name>instance.secret</name>
+ <value>DEFAULT</value>
+</property>
+
+The instance needs a secret to enable secure communication between servers. Configure your
+secret and make sure that the +accumulo-site.xml+ file is not readable to other users.
++For alternatives to storing the +instance.secret+ in plaintext, please read the
+++Sensitive Configuration Values+ section.
+
+Some settings can be modified via the Accumulo shell and take effect immediately, but
+some settings require a process restart to take effect. See the configuration documentation
+(available in the docs directory of the tarball and in <<configuration>>) for
details.
+
+==== Deploy Configuration
+
+Copy the masters, slaves, accumulo-env.sh, and if necessary, accumulo-site.xml
+from the +$ACCUMULO_HOME/conf/+ directory on the master to all the machines
+specified in the slaves file.
+
++==== Sensitive Configuration Values
++
++Accumulo has a number of properties that can be specified via the accumulo-site.xml
++file which are sensitive in nature, instance.secret and trace.token.property.password
++are two common examples. Both of these properties, if compromised, have the ability
++to result in data being leaked to users who should not have access to that data.
++
++In Hadoop-2.6.0, a new CredentialProvider class was introduced which serves as a common
++implementation to abstract away the storage and retrieval of passwords from plaintext
++storage in configuration files. Any Property marked with the +Sensitive+ annotation
++is a candidate for use with these CredentialProviders. For version of Hadoop which lack
++these classes, the feature will just be unavailable for use.
++
++A comma separated list of CredentialProviders can be configured using the Accumulo Property
+++general.security.credential.provider.paths+. Each configured URL will be consulted
++when the Configuration object for accumulo-site.xml is accessed.
++
++==== Using a JavaKeyStoreCredentialProvider for storage
++
++One of the implementations provided in Hadoop-2.6.0 is a Java KeyStore CredentialProvider.
++Each entry in the KeyStore is the Accumulo Property key name. For example, to store the
++\texttt{instance.secret}, the following command can be used:
++
++ hadoop credential create instance.secret --provider jceks://file/etc/accumulo/conf/accumulo.jceks
++
++The command will then prompt you to enter the secret to use and create a keystore in:
++
++ /etc/accumulo/conf/accumulo.jceks
++
++Then, accumulo-site.xml must be configured to use this KeyStore as a CredentialProvider:
++
++[source,xml]
++<property>
++ <name>general.security.credential.provider.paths</name>
++ <value>jceks://file/etc/accumulo/conf/accumulo.jceks</value>
++</property>
++
++This configuration will then transparently extract the +instance.secret+ from
++the configured KeyStore and alleviates a human readable storage of the sensitive
++property.
++
+=== Initialization
+
+Accumulo must be initialized to create the structures it uses internally to locate
+data across the cluster. HDFS is required to be configured and running before
+Accumulo can be initialized.
+
+Once HDFS is started, initialization can be performed by executing
++$ACCUMULO_HOME/bin/accumulo init+ . This script will prompt for a name
+for this instance of Accumulo. The instance name is used to identify a set of tables
+and instance-specific settings. The script will then write some information into
+HDFS so Accumulo can start properly.
+
+The initialization script will prompt you to set a root password. Once Accumulo is
+initialized it can be started.
+
+=== Running
+
+==== Starting Accumulo
+
+Make sure Hadoop is configured on all of the machines in the cluster, including
+access to a shared HDFS instance. Make sure HDFS and ZooKeeper are running.
+Make sure ZooKeeper is configured and running on at least one machine in the
+cluster.
+Start Accumulo using the +bin/start-all.sh+ script.
+
+To verify that Accumulo is running, check the Status page as described in
+<<monitoring>>. In addition, the Shell can provide some information about the
status of
+tables via reading the metadata tables.
+
+==== Stopping Accumulo
+
+To shutdown cleanly, run +bin/stop-all.sh+ and the master will orchestrate the
+shutdown of all the tablet servers. Shutdown waits for all minor compactions to finish,
so it may
+take some time for particular configurations.
+
+==== Adding a Node
+
+Update your +$ACCUMULO_HOME/conf/slaves+ (or +$ACCUMULO_CONF_DIR/slaves+) file to account
for the addition.
+
+ $ACCUMULO_HOME/bin/accumulo admin start <host(s)> {<host> ...}
+
+Alternatively, you can ssh to each of the hosts you want to add and run:
+
+ $ACCUMULO_HOME/bin/start-here.sh
+
+Make sure the host in question has the new configuration, or else the tablet
+server won't start; at a minimum this needs to be on the host(s) being added,
+but in practice it's good to ensure consistent configuration across all nodes.
+
+==== Decomissioning a Node
+
+If you need to take a node out of operation, you can trigger a graceful shutdown of a tablet
+server. Accumulo will automatically rebalance the tablets across the available tablet servers.
+
+ $ACCUMULO_HOME/bin/accumulo admin stop <host(s)> {<host> ...}
+
+Alternatively, you can ssh to each of the hosts you want to remove and run:
+
+ $ACCUMULO_HOME/bin/stop-here.sh
+
+Be sure to update your +$ACCUMULO_HOME/conf/slaves+ (or +$ACCUMULO_CONF_DIR/slaves+) file
to
+account for the removal of these hosts. Bear in mind that the monitor will not re-read the
+slaves file automatically, so it will report the decomissioned servers as down; it's
+recommended that you restart the monitor so that the node list is up to date.
+
+[[monitoring]]
+=== Monitoring
+
+The Accumulo Master provides an interface for monitoring the status and health of
+Accumulo components. The Accumulo Monitor provides a web UI for accessing this information
at
++http://_monitorhost_:50095/+.
+
+Things highlighted in yellow may be in need of attention.
+If anything is highlighted in red on the monitor page, it is something that definitely needs
attention.
+
+The Overview page contains some summary information about the Accumulo instance, including
the version, instance name, and instance ID.
+There is a table labeled Accumulo Master with current status, a table listing the active
Zookeeper servers, and graphs displaying various metrics over time.
+These include ingest and scan performance and other useful measurements.
+
+The Master Server, Tablet Servers, and Tables pages display metrics grouped in different
ways (e.g. by tablet server or by table).
+Metrics typically include number of entries (key/value pairs), ingest and query rates.
+The number of running scans, major and minor compactions are in the form _number_running_
(_number_queued_).
+Another important metric is hold time, which is the amount of time a tablet has been waiting
but unable to flush its memory in a minor compaction.
+
+The Server Activity page graphically displays tablet server status, with each server represented
as a circle or square.
+Different metrics may be assigned to the nodes' color and speed of oscillation.
+The Overall Avg metric is only used on the Server Activity page, and represents the average
of all the other metrics (after normalization).
+Similarly, the Overall Max metric picks the metric with the maximum normalized value.
+
+The Garbage Collector page displays a list of garbage collection cycles, the number of files
found of each type (including deletion candidates in use and files actually deleted), and
the length of the deletion cycle.
+The Traces page displays data for recent traces performed (see the following section for
information on <<tracing>>).
+The Recent Logs page displays warning and error logs forwarded to the monitor from all Accumulo
processes.
+Also, the XML and JSON links provide metrics in XML and JSON formats, respectively.
+
+==== SSL
+SSL may be enabled for the monitor page by setting the following properties in the +accumulo-site.xml+
file:
+
+ monitor.ssl.keyStore
+ monitor.ssl.keyStorePassword
+ monitor.ssl.trustStore
+ monitor.ssl.trustStorePassword
+
+If the Accumulo conf directory has been configured (in particular the +accumulo-env.sh+
file must be set up), the +generate_monitor_certificate.sh+ script in the Accumulo +bin+ directory
can be used to create the keystore and truststore files with random passwords.
+The script will print out the properties that need to be added to the +accumulo-site.xml+
file.
+The stores can also be generated manually with the Java +keytool+ command, whose usage can
be seen in the +generate_monitor_certificate.sh+ script.
+
+If SSL is enabled, the monitor URL can only be accessed via https.
+This also allows you to access the Accumulo shell through the monitor page.
+The left navigation bar will have a new link to Shell.
+An Accumulo user name and password must be entered for access to the shell.
+
+[[tracing]]
+=== Tracing
+It can be difficult to determine why some operations are taking longer
+than expected. For example, you may be looking up items with very low
+latency, but sometimes the lookups take much longer. Determining the
+cause of the delay is difficult because the system is distributed, and
+the typical lookup is fast.
+
+Accumulo has been instrumented to record the time that various
+operations take when tracing is turned on. The fact that tracing is
+enabled follows all the requests made on behalf of the user throughout
+the distributed infrastructure of accumulo, and across all threads of
+execution.
+
+These time spans will be inserted into the +trace+ table in
+Accumulo. You can browse recent traces from the Accumulo monitor
+page. You can also read the +trace+ table directly like any
+other table.
+
+The design of Accumulo's distributed tracing follows that of
+http://research.google.com/pubs/pub36356.html[Google's Dapper].
+
+==== Tracers
+To collect traces, Accumulo needs at least one server listed in
+ +$ACCUMULO_HOME/conf/tracers+. The server collects traces
+from clients and writes them to the +trace+ table. The Accumulo
+user that the tracer connects to Accumulo with can be configured with
+the following properties
+
+ trace.user
+ trace.token.property.password
+
+==== Instrumenting a Client
+Tracing can be used to measure a client operation, such as a scan, as
+the operation traverses the distributed system. To enable tracing for
+your application call
+
+[source,java]
+DistributedTrace.enable(instance, new ZooReader(instance), hostname, "myApplication");
+
+Once tracing has been enabled, a client can wrap an operation in a trace.
+
+[source,java]
+Trace.on("Client Scan");
+BatchScanner scanner = conn.createBatchScanner(...);
+// Configure your scanner
+for (Entry entry : scanner) {
+}
+Trace.off();
+
+Additionally, the user can create additional Spans within a Trace.
+
+[source,java]
+Trace.on("Client Update");
+...
+Span readSpan = Trace.start("Read");
+...
+readSpan.stop();
+...
+Span writeSpan = Trace.start("Write");
+...
+writeSpan.stop();
+Trace.off();
+
+Like Dapper, Accumulo tracing supports user defined annotations to associate additional
data with a Trace.
+
+[source,java]
+...
+int numberOfEntriesRead = 0;
+Span readSpan = Trace.start("Read");
+// Do the read, update the counter
+...
+readSpan.data("Number of Entries Read", String.valueOf(numberOfEntriesRead));
+
+Some client operations may have a high volume within your
+application. As such, you may wish to only sample a percentage of
+operations for tracing. As seen below, the CountSampler can be used to
+help enable tracing for 1-in-1000 operations
+
+[source,java]
+Sampler sampler = new CountSampler(1000);
+...
+if (sampler.next()) {
+ Trace.on("Read");
+}
+...
+Trace.offNoFlush();
+
+It should be noted that it is safe to turn off tracing even if it
+isn't currently active. The +Trace.offNoFlush()+ should be used if the
+user does not wish to have +Trace.off()+ block while flushing trace
+data.
+
+==== Viewing Collected Traces
+To view collected traces, use the "Recent Traces" link on the Monitor
+UI. You can also programmatically access and print traces using the
++TraceDump+ class.
+
+==== Tracing from the Shell
+You can enable tracing for operations run from the shell by using the
++trace on+ and +trace off+ commands.
+
+----
+root@test test> trace on
+
+root@test test> scan
+a b:c [] d
+
+root@test test> trace off
+Waiting for trace information
+Waiting for trace information
+Trace started at 2013/08/26 13:24:08.332
+Time Start Service@Location Name
+ 3628+0 shell@localhost shell:root
+ 8+1690 shell@localhost scan
+ 7+1691 shell@localhost scan:location
+ 6+1692 tserver@localhost startScan
+ 5+1692 tserver@localhost tablet read ahead 6
+----
+
+=== Logging
+Accumulo processes each write to a set of log files. By default these are found under
++$ACCUMULO/logs/+.
+
+=== Recovery
+
+In the event of TabletServer failure or error on shutting Accumulo down, some
+mutations may not have been minor compacted to HDFS properly. In this case,
+Accumulo will automatically reapply such mutations from the write-ahead log
+either when the tablets from the failed server are reassigned by the Master (in the
+case of a single TabletServer failure) or the next time Accumulo starts (in the event of
+failure during shutdown).
+
+Recovery is performed by asking a tablet server to sort the logs so that tablets can easily
find their missing
+updates. The sort status of each file is displayed on
+Accumulo monitor status page. Once the recovery is complete any
+tablets involved should return to an ``online'' state. Until then those tablets will be
+unavailable to clients.
+
+The Accumulo client library is configured to retry failed mutations and in many
+cases clients will be able to continue processing after the recovery process without
+throwing an exception.